In an integrated circuit (IC), it is sometimes desirable to include an on-board testing apparatus which runs a diagnostic test of other circuitry on the IC. A TEST signal, which is generated externally, must be delivered to the testing apparatus, in order to initiate the testing sequence. A connector pin of the IC must carry the TEST signal. However, it is not desirable to permanently dedicate one (or more) of the connector pins to this TEST signal, because (a) pins on ICs are expensive, (b) they are in demand for other functions, and (c) the diagnostic testing is performed infrequently, compared with the other functions for which the IC was designed, so that the dedicated pin would remain idle most of the time.